diff --git a/Source/exehead/util.c b/Source/exehead/util.c
index ef8f3056..35249002 100644
--- a/Source/exehead/util.c
+++ b/Source/exehead/util.c
@@ -891,7 +891,7 @@ WIN32_FIND_DATA * NSISCALL file_exists(char *buf)
   return NULL;
 }
 
-void * NSISCALL myGetProcAddress(char *dll, char *func)
+void * NSISCALL myGetProcAddress(const char *dll, const char *func)
 {
   HMODULE hModule = GetModuleHandle(dll);
   if (!hModule)
diff --git a/Source/exehead/util.h b/Source/exehead/util.h
index 19257f6b..e3ae6d39 100644
--- a/Source/exehead/util.h
+++ b/Source/exehead/util.h
@@ -91,7 +91,7 @@ void NSISCALL MoveFileOnReboot(LPCTSTR pszExisting, LPCTSTR pszNew);
 void NSISCALL mini_memcpy(void *out, const void *in, int len);
 void NSISCALL remove_ro_attr(char *file);
 
-void * NSISCALL myGetProcAddress(char *dll, char *func);
+void * NSISCALL myGetProcAddress(const char *dll, const char *func);
 void NSISCALL MessageLoop(UINT uCheckedMsg);
 
 // Turn a pair of chars into a word